1. Field of the Invention
The invention relates in general to a sample rate converter, and more particularly to a sample rate converter capable of adaptively changing an operation configuration thereof.
2. Description of the Related Art
With continual progresses in electronics-related technologies, various kinds of communications apparatuses have become more and more common. Transmitters or receivers in current communication apparatuses frequently include front-end analog circuits and rear-end digital circuits. Between the two circuits with different signal types is provided with a digital-to-analog converter (DAC) or an analog-to-digital converter (ADC).
FIG. 1 shows a simple function block diagram of transmitting circuits used in a 3rd-Generatation Partnership Project (3GPP) communication device. To prevent high-order harmonics of pulses in a digital signal from causing interferences on an analog circuit, the digital circuit 120 and the analog circuit 160 are usually physically spaced by a protection distance for guarding against coupling interference. In addition, to further reduce possible negative influences that the high-order harmonics in the digital pulses pose on the analog circuit 160, a transmission signal 110 first is processed by a sample rate converter 122 before entering a DAC 140. The sample rate of an up-converted signal 130 outputted by the sample rate converter 122 is equal to a quotient of dividing an operation sample rate of the analog circuit 160 by a predetermined integer. In other words, the operation sample rate of the analog circuit 160 is an integral multiple of the sample rate of the up-converted signal 130. Similarly, a digital signal of a 3GPP receiver (not shown) also includes a sample rate converter that down-converts an input signal.
Known to one person skilled in the art, the accuracy of a conversion result of a sample rate converter is related to an order of the converter sample rate. A high-order sample rate converter includes larger quantities of circuit elements and computation procedures to provides more ideal conversion results but to cause greater power consumption. Further, an ambient environment that a communication device encounters usually constantly changes with time. To maintain normal operations in harsh communication environments (e.g., environments with large amounts of noises and interferences), a high-order sample rate converter in a communication device is mostly used. For a mobile communication device, high power consumption caused by a high-order sample rate converter is an unfavorable factor that may shorten a standby period of the mobile communication device.